Process for improving aluminium alloys by heating and chilling.



No. 868,383. PATENTED OCT. 15, 1907. P. G. A. WILM.

PROCESS FOR IMPROVING ALUMINIUM ALLOYS BY HEATING AND GI'IILLING.

APPLICATION FILED 00'1.1'l, 1905.

WITNESSES INVENTOR A TTOHNE YS FERDINAND GUSTAV ALFRED WILM, OF DREWITZ,GERMANY.

PROCESS FOR IMPROVING ALUMINIUM ALLOYS BY HEATING AND CHILLING.

Specification of Letters Patent.

PatentedOet. 15, 1907.

Application filed October 17,1905. Serial No. 283,197-

I pletely altered in their technological qualities by rapidly coolingthe same when they are heated to a certain degree of temperature andthat comprehensive use is made of this fact in the arts, as for instancein steel-hardening.

With regard to the application of chilling in the art of casting and themanufacture of aluminium-alloys no success of any practical importancehas resulted up to this day. Now the applicant has succeeded indeveloping the rapid-cooling process to a degree of perfection allowingof its general application to the manufacture of aluminium-alloys, sothat the strength and the ductility are considerably increased in suchalloys by rapidly cooling (or chilling) the same from a certaincharacteristic and physicallywell defined temperature to a lower degreeof temperature.

All particular circumstances and characteristic features of the presentrefining method may be explained in considering alloys of aluminium withcopper. As a matter of course it may only be mentioned that the refiningprocess embodying the present invention is logically applicable also toother aluminium-alloys.

From numerous experimental trials and observations it has been foundthat all alloys of aluminium and copper have a certain critical point oftemperature, which is called the recalescence point and becomes apparentby sudden emanation of heat whenever an alloy of the respective kind iscooleddowir from a higher temperature to a considerably lower one; andas to methods for determining such critical temperature-points (whichhave been observed for the first time in treating iron), theirexplanation being beyond the scope of the present invention may besupposed as known matter. It may be suggested only to the reader that asynoptic treatise on methods of determining recalescence-points is thatof Guillet bearing the title: lies alliages mtalliques.

In the diagram annexed to this specification t e situation of therecalescence point is indies: ed In! any percentage of copper intlwaluminiuiu-all =y 111; showess is performed by heating during acertain lapse of time the aluminium-alloy at a temperature, which issituated in the temperature interval between its solidification-pointand a temperature being 30 centigrade below the recalescence point, andby rapidly cooling (or chilling) the ingot or object brought to thistemperature- It is admissible to go below the recalescence point by somedegrees (in practice 30 degrees have been found admissible) as aconversion succes sively takes place. It is not necessary that thetemperature, from which the metal is chilled, coincides with thetemperature to which the metal is first heated. It is only necessarythat the temperature from which the alloy is chilled, is never situatedat a lower point than 30$ centrigrade below the recalescencetemperature. Considering for instance an aluminium-alloy containing 4%of copper, its refining temperature is situated between 5253 0495centigrade and its solidification point of 640 centigrade.

The cooling or chilling operation may be effected by using water ofnormal temperature.

In case of chill-castings of an aluminium-alloy containing 4% of coppermade with application of the present refining method the tensilestrength has, been increased from 15.5 to 22.9 kg sq in m and theelongation approximately from 5% to 7%. Almost the same increase of thetensile strength has been stated in the examination of sand-castingswhich have been made with the same aluminium-coppcr-alloy. Whenexamining the same aluminium-alloy with 4% of copper, after it had beenrolled and refined until increasing its tensile strength to 27.9 kg sqm-m, its elongation has been augmented from about 2.6% to 17.3%.Comparing these results to that obtained by annealing the same rolledmaterial to 220 centigrade, following to that ef feet the usual process,it has been observed that the tensile strength was reduced by 3.4 kg sqin in, when an increase of 2.6% to-only 7.8% had been obtained inelongation.

In treating by the refining process an alloy to which by mechanicallyWorking the same the highest attainable degree of strength had beenimparted, a very considerable increase of the ductility (elongation) wasobtained, which was not accompanied by an observable diminution of thetensile strength, whereas the usual process of annealing causes a veryconsiderable diminution of the tensile strength.

By the following table I suggest a record of the recal- 5 escence pointsas they have been determined for a series of differentalurninium-copper-alloys Percentage Recalescence of copper: 1.temperature: 485 Centigrade. l 2- I! K Y 3. 512 H 4 l H i 6 l U I l I Itis obvious that the present refining-process is available both forfinished castings or work-pieces or the like and for ingots and blocksof metal-alloys, the latter being subjected after the refiningoperation-to working by rolling or hammer-mills etc. In particular itwill be ent is:

The herein described method of refining aluminium alloys which consistsin heating said alloy to a point immediately under its fusingtemperature, and then chilling such alloy at a temperature lying betweenthe fusing temperature of that alloy and a temperature lying not over 30below the point of recalescence of that alloy substantially asdescribed.

in testimony whereof have signed name to this specifics-l tion in thepresence of two subscribing witnesses.

FERDINAND GUSTAV ALFRED WILM.

Witnesses:

\VoLDmrAn HAUP'i, HENRY HASPER.

What I claim and desire to secure by Letters Pat-

